In the field of microelectronic chip packages, greater performance is obtained through continuous increase of power density, leading to continuous increase in rate of heat removal required (Mahajan et al. 2006). Thermal resistance at the interface between the chip package and a cooling device is a major impediment to heat removal. This thermal resistance is typically reduced by insertion of a thermal interface material (“TIM”). Thermal interface material layers are typically formed by pressing the thermal interface material between a flat surface of the microprocessor chip and a flat surface of a cooling device. A typical TIM is a polymeric liquid which is filled to a large volume fraction with micron-size solid particles.
Such TIMs conduct heat better when highly filled with solid particles, but such filling substantially increases the TIM effective viscosity and yield stress. Thin layers of TIM are desired for low thermal resistance, but formation of such thin layers by squeezing flow can require dangerously large forces and long squeezing times, due to the increased effective viscosity and yield stress of a highly-filled TIM. There exists a need to form thinner layers of such TIMs more rapidly, with reduced squeezing force.
Brunschwiler et al. (US 200610286712 A1) achieve this aim by cutting channels in the surfaces of the microprocessor chip and/or the cooling device. Such cutting of channels requires additional manufacturing time and expense.
It is the aim of the present invention to provide a method of forming thinner TIM layers more rapidly, with reduced squeezing force, and to avoid a requirement for modifying the microprocessor chip and/or cooling device.